Heat pump system air conditioners

ABSTRACT

A heat pump-type air conditioner which is so designed that a lack of heating capacity in the heating operation when the outdoor temperature is low in winter is supplemented by refrigerant heating means consisting of an electric heater provided at an intermediate position of the refrigerant passage line of an indoor heat exchanger for heating the refrigerant to provide for recondensation of the refrigerant which has once been condensed; in the heating operation the refrigerant in the refrigeration cycle is decreased from the quantity used in the cooling operation and maintained in a quantity optimum for the heating operation; and further defrosting of an outdoor heat exchanger can quickly be attained; and which can be operated efficiently with no fear of fire.

United States Patent [21] Appl. No. [22] Filed [45} Patented [73]Assignee Priority HEAT PUMP SYSTEM AIR CONDITIONERS 10 Claims, 12Drawing Figs.

US. Cl 165/29, 165/64, 62/324 Int. Cl. F25b 29/00 Field of Search165/26, 29, 64; 12/324 [56] References Cited UNITED STATES PATENTS3,308,877 3/1967 Gerteis 165/29 Primary ExaminerChar1es SukaloAltorney-Cushman, Darby & Cushman ABSTRACT: A heat pump-type airconditioner which is so designed that a lack of heating capacity in theheating operation when the outdoor temperature is low in winter issupplemented by refrigerant heating means consisting of an electricheater provided at an intermediate position of the refrigerant passageline of an indoor heat exchanger for heating the refrigerant to providefor recondensation of the refrigerant which has once been condensed; inthe heating operation the refrigerant in the refrigeration cycle isdecreased from the quantity used in the cooling operation and maintainedin a quantity optimum for the heating operation; and further defrostingof an outdoor heat exchanger can quickly be attained; and which can beoperated efficiently with no fear of fire.

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INVl-ZNTORS 4.5 5 51 W M ATTORNEYS FIGS @IHIIIIIIIIYIIILlfllllfillulllllllll HEAT PUMP SYSTEM AIR CONDITIONERS A conventionalheat pump system air conditioner which is singly usable for both coolingand heating by operating the refrigeration cycle in one way or another,involves a number of problems when used as a heater because ofdifferences in the inside volumes of the evaporator and condenser, thearea of the heat exchangers and the rate of air passing in the heatexchanger, between the heating operation and the cooling operation,which occur as a result of operating the refrigeration cycle in areverse way, and also because of the temperature and the moisture of theroom to be heated, the outdoor temperature and moisture conditions andthe use of different elements such as an auxiliary heater andcontroller. Namely,

I. Since the evaporating temperature lowers with the out doortemperature in winter, the function of the compressor is degraded.Therefore, the heating capacity which resorts to the condensation of therefrigerant in the indoor heat exchanger is lowered.

2 An increasing temperature difference between the indoor and outdoor,caused by lowering of the outside temperature in winter results in anincreasing heating load, while on the 'other hand, the heating capacityis lowered as stated in l above. Consequently, the lack of heatingcapacity increases as the outside temperature drops. I 1 l 3. In orderto make up the lack of heating capacity in winter, it has been a commonpractice to provide an electric heater on the indoor heat exchanger anduse only the electric heater in the heating operation, or to operatesaid electric heater and the heat pump system air conditionersimultaneously in the heating operation. However, the use of the elec'tric heater provides a cause of fire. 4. The heating operation requiresa less quantity of refrigerant than required in the cooling operation.Therefore, in the heating operation the heating efficiency of the airconditioner is degraded by excess refrigerant residing in the respectiveelements or the excess refrigerant flows into the compressor causingfailure of the same.

5. in the heating operation in winter, when the outside temperaturedrops, the evaporating temperature is lowered and the surfacetemperature of the outdoor heat exchanger drops below the freezingpoint. Thus, the surface of the outdoor heat exchanger is frosted. Thefrosting of the outdoor heat exchanger causes a lowering of the heatexchanging efficiency and accelerates the lowering of evaporatingtemperature, and at the same time, encourages frosting of the outdoorheat exchanger, with the eonsequency that the air conditioner becomesinoperative.

As stated above, when the air conditioner is used as a heater in winter,the heating capacity is lowered, whereas the heating load is increasedas the outside temperature drops, and thus the heating capacity becomesshorted. In order to deal with such problem, a method has been employedin which the heat pump is held inoperative and the electric heater oflarge capacity only is operated for heating which is provided on theindoor heat exchanger. This method, however, adds to the expense for theheating operation and requires a large space to be provided for mountingthe electric heater, which makes the apparatus large in size. Moreover,since the heated surface of the electric heater is exposed to directlyheat air, there is the danger of fire when inflammables such as paper orcloth are casually brought into contact with the electric heater or whenthe heat-insulating material attached to the outer panel of theconditioner is delaminated therefrom during use of the conditioner andgets close to the electric heater, if such heat insulating material iscombustible. Additionally, a safety device such as a thermostate, usedin the conventional air conditioner of the type described, is notsufficiently reliable due to the fact that it detects the criticaltemperature with intervention of air. This also provides a danger offire. Another method which has been employed heretofore is to provide anelectric heater of small capacity on the indoor heat exchanger, whichgenerates heat just sufi'lcient enough to make up the lack of heatingcapacity of the conditioner. This method is again unsatisfactory inrespect of danger of fire, because the electric heater directly heatsair.

Now, concerningthe various troubles resultingfrom the difference inquantity of the refrigerant required for the heating operation and thecooling operation, there have been proposed a number of refrigerantregulating means. However, such refrigerant regulating means areunexceptionally only capable of maintaining a required quantity ofrefrigerant in the cooling operation or in the heating operation andonly render the construction of the conditioner unnecessarilycomplicated and the size of the same unnecessarily large.

Concerning the problem of the outdoor heat exchanger being frosted inthe heating operation when the outside temperature is low in winter,there has been employed a method in which the refrigeration cycle of theconditioner is switched to the cooling operation when the frost attachedto the outdoor heat exchanger has reached a predetermined quantity,thereby to remove the frost. This method, however, is defective in thatsince the indoor heat exchanger operates as evaporator in the period ofdefrosting operation, the air circulating within the room is cooled bythe indoor heat exchanger and blown against the person or persons in theroom, giving the person or persons a chill. In order to avoid suchdisadvantage, it has been practiced to stop or decrease the draft intothe room during the defrosting operation. In this case, the air passingthrough the indoor heat exchanger is reduced to none or decreased andaccordingly the heat absorption from the air inside the room is stoppedor decreased. This results in a reduction of heat radiated by theoutdoor heat exchanger or, in other words, the defrosting efficiency isdegraded, necessitating a lengthy period of time to be required fordefrosting. In this method, the air inside the room is also cooled byboth the indoor heat exchanger and the outer panel of the conditioner,though the cold draft into the room is stopped or decreased, and hencethe inside temperature of the room is lowered to below the comforablelimit, which has been the fatal drawback of the method.

The present invention is to obviate the drawbacks of the conventionalair conditioners as set forth above. Namely, the first object of theinvention is to provide a heat pump system air conditioner utilizingrefrigeration cycle, in which refrigerant-heating means consisting of anelectric heater, not exposed to air, is provided at an intermediateposition of the refrigerant passage line of an indoor heat exchanger forheating a refrigerant, thereby to form in the heating operation such arefrigeration cycle wherein a high-pressure superheated gas, dischargedfrom a compressor, is partially or wholly condensed and liquefied at aportion of the indoor heat exchanger into a wet vapor and after the wetvapor is reevaporated by the refrigerant-heating means, the resultantgas is again condensed and liquefied at the remaining portion of theindoor heat exchanger, the subcooling refrigerant thus liquefied flowinginto an expansion member wherein it is reduced in pressure, and thenevaporated and gasified in an outdoor heat exchanger and returned intothe compressor, whereby a lack of heating capacity occurring when theoutside temperature is low in winter can be supplemented, with no fearof fire since the electric heater is not exposed to air as is in theconventional conditioners.

The second object of the invention is to provide a heat pump system airconditioner of the character described above, in which saidrefrigerant-heating means is provided extending therethrough with amounting tube or tubes having one end open to the outside of one end ofone end of the refrigerantheating means and the other end closed or opento the outside of the other end of said refrigerant-heating means, inwhich are disposed an electric heater and an overheat preventing memberconsisting of a thermostat or a temperature fuse which is provided forthe purpose of preventing the refrigerant from being decomposed ordeteriorated by contact with the outer peripheral surface of saidmounting tube when the temperature of said mounting tube becomesabnormally high, whereby mounting of said parts in the mounting tube andreplacement of the same due to failure are facilitated.

The third object of the invention is to provide a heat pump system airconditioner of the character described above, in which said mountingtube in said refrigerant heating means is provided with fins on theouter peripheral surface thereof which is in contact with therefrigerant, so as to lower the temperature of said surface and therebyto prevent decomposition and deterioration of the refrigerant by theheat of the mounting tube and also to increase the refrigerant-heatingsurface area to heat the refrigerant effectively and moderately Thefourth object of the invention is to provide a heat pump system airconditioner of the character described above, in which an electriccircuit of the air conditioner is so designed that the electric heaterof said refrigerant-heating means will be actuated, in the heatingoperation, only when said compressor is in operation, whereby localheating of the refrigerant by the electric heater when the refrigerantis held stationary upon deenergization of the compressor can be avoidedand hence the danger of the refrigerant partially being decomposed anddeteriorated is eliminated.

The fifth object of the invention is to provide a heat pump system airconditioner of the character described above, in which the electriccircuit of the air conditioner is so designed that therefrigerant-heating means is held energized, not only during the normalheating operation but also during a defrosting operation for eliminatingthe frost attached to the outdoor heat exchanger, which is effectuatedby the cooling cycle, whereby the refrigerant present in the indoor heatexchanger, which acts as evaporator in the defrosting operation, isheated to elevate the evaporating temperature thereof and to prevent thesurface temperature of said indoor heat exchanger from lowering tothereby avoid a cold draft blowing into the room, and also thedefrosting period is shortened as a result of the condensationtemperature in the outdoor heat exchanger being elevated by theevaporating temperature rise.

The sixth object of the invention is to provide a heat pump system airconditioner of the character described above, in which said electricheater for heating the refrigerant is directly inserted into therefrigerant of the refrigerant-heating means and the danger ofelectricity leakage is avoided by making use of the electricityinsulating effect of the refrigerant.

The seventh object of the invention is to provide heat pump system airconditioner of the character described above, in which in the heatingoperation the refrigerant is supplied into the refrigerant-heating meansthrough a conduit communicating with the lower portion of the cavity inthe refrigerant-heating means and discharged through a conduitcommunicating with the upper portion of the same, so that excessrefrigerant may be stored in said refrigerant-heating means in theliquid form during the heating operation, whereby the necessity forproviding a separate refrigerant storage tank can be eliminated and therefrigerant is heated efiieiently by the electric heater during itsresidence in said refrigerant-heating means, enabling the effect ofheating the refrigerant to be fully demonstrated, which is the firstobject of the present invention.

The eighth object of the invention is to provide a heat pump system airconditioner of the character described above, particularly in thepreceding paragraph, in which when the outdoor heat exchanger has beenfrosted, the refrigeration cycle is switched from the heating cycle tothe cooling cycle, whereupon the pressure inside the refrigerant heatingmeans is reduced and the liquid refrigerant stored therein is evaporatedabruptly and sucked into the compressor, and thus the introduction ofthe refrigerant gas into and discharge of the compressed refrigerant gasfrom the compressor can smoothly be effected and the defrosting periodcan be shortened ac cordingly.

The ninth object of the invention is to provide a heat pump system airconditioner of the character described above, in which the electriccircuit of the air conditioner is so designed that a fan is rotated at alow speed when the temperature of the discharging air is low at thestart of the heating operation and is rotated at a high speed when thetemperature of the discharging air has reached to a desired level, sothat air is blown into the room at a low rate in the initial state ofthe heating operation when the condensation temperature of therefrigerant in the indoor heat exchanger is low and the temperature ofthe air discharged from the air conditioner is low, so as to minimizethe undesirable effect of cold draft, whereas when the condensationtemperature in the indoor heat exchanger has risen sufficiently and thetemperature of the air blown into the room has been elevated high enoughnot to cause cold draft, the rotational speed of the fan is increased topromote heating of the room.

The tenth object of the invention is to provide a heat pump system airconditioner of the character described above, in which the electriccircuit of the air conditioner is so designed that the electric heaterprovided in the refrigerant-heating means will be energized, in theheating operation, only when the room temperature is low and will not beenergized when the room temperature is high, so that said electricheater may effectively utilized.

These and other objects, advantages and features of the invention willbe more clearly understood from the following detailed description whentaken in conjunction with the accompanying drawings, in which:

HO. 1 is a piping diagram of the refrigeration cycle of the heat pumpsystem air conditioner according to the present invention;

FIG. 2 is a mollier diagram of the air conditioner;

FIG. 3 is an electric wiring diagram ofthe air conditioner;

FIG. 4 is a schematic view showing the construction of the airconditioner;

FIG. 5 is a cross-sectional view of one form of the refrigerant-heatingmeans comprising a mounting tube or tubes, and an electric heater and anoverheat preventing member disposed in each mounting tube, and having ahigher conduit and a lower conduit connected horizontally to theopposite end walls of said refrigerant-heating means;

FIG. 6 is a cross-sectional view of another form of therefrigerant-heating means comprising a mounting tube or tubes and anelectric heater disposed in each mounting tube, and having a lowerconduit and a higher conduit connected vertically to both end portionsof the refrigerant-heating unit;

FIG. 7 is a cross-sectional view of still another form of therefrigerant-heating means comprising a mounting tube or tubes and anelectric heater disposed in each mounting tube, and having two lowerconduits connected in parallel relation to both end portions of therefrigerant-heating means and a higher conduit connected to the centralportion of the refrigerant-heating means;

FlG. 8 is a cross-sectional view of still another form of therefrigerant-heating means comprising a mounting tube or tubes and anelectric heater directly wound on each mounting tube;

FIGS, 9 to 12 are diagrams respectively showing the characteristics ofthe air conditioner, in which FIG. 9 is a heating capacitycharacteristic diagram showing the relationship between the outdoortemperature, and the power consumption and the heating capacity;

FIG. 10 is a liquid refrigerant storage effect characteristic of therefrigerant-heating means diagram showing the relationship between theoutdoor temperature and the gas intake tube temperature;

H6. 11 is a defrosting test characteristic diagram showing therelationship between the time elapsed in the operation and thedischarging air temperature; and

FIG. 12 is an overheat preventing member of the refrigerant heatingmeans operation test characteristic diagram showing the relationshipbetween the time elapsed after the stoppage of the compressor and thefan and the temperature.

Referring to FlGS. l and 2, the path of the refrigerant in heatingoperation forms a refrigeration refrigerant-heating as indicated by thesolid line arrows which extends from a compressor l to four-waychangeover valve 2, a first indoor heat exchanger 3, a lower conduit 10,a refrigerant-heating means 6, a higher conduit ill, a second indoorheat exchanger 3", a capillary tube 4, an outdoor heat exchanger 5, thefour-way changeover valve 2, an accumulator l4! and back to thecompressor 1, and in the cooling operation, forms a reverserefrigeration cycle as indicated by the dotted line arrows, with theposition of the four-way changeover valve 2 being changed uponenergization of the electromagnetic coil thereof.

A refrigerant heating means 6 is provided at an intermediate positionbetween the first indoor heat exchanger 3' and the second indoor heatexchanger 3" which together form an indoor heat exchanger 3.

In the heating operation, the high temperature, high-pressurerefrigerant gas discharged from the compressor ll (condition B in FIG.2) is sent through the four-way changeover valve 2 into the first indoorheat exchanger 3', wherein it is partially condensed to form a wet vapor(condition C in F [v 2) while imparting heat to the indoor, and thenadmitted into the refrigerant-heating means 6. The gaseous refrigerantflows through the refrigerant-heating means 6 but the liquid refrigerantis accumulated in the refrigerant-heating means and heated by anelectric heater 7 provided therein and partially evaporated (condition Din FIG. 2). The resultant gas liquid mixture of the coolant, leaving therefrigerant-heating means 6, enters the second indoor heat exchanger 3",wherein the gaseous refrigerant is condensed again (condition E in FIG.2) while imparting heat to the indoor, and then proceeds into thecapillary 4l. Thereafter, the refrigerant passes through the outdoorheat exchanger 5 (condition F in FIG. 2), the four-way changeover valve2 and the accumulator l4, and returns to the compressor 1 (condition Ain FIG. 2). The refrigerant may be entirely liquefied in the firstindoor heat exchanger 3, instead of being partially liquefied as statedabove.

The refrigerant-heating means 6 will be described in detail hereunder:

Referring to FIG. 5, the refrigerant-heating means 6 thereshown has amounting tube 8 extending through the center thereof, and an electricheater 7 is inserted into the mounting tube 6 through one end, while anoverheat-preventing member 9, such as a thermostat or a temperaturefuse, is inserted into the tube through the other end, whichautomatically controls the current supply to the electric heater 7 upondetecting the temperature of the mounting tube 8. Numeral l3 designatesfins provided on the outer peripheral surface of the mounting tube 8 toincrease the heat-exchanging area.

To the lower portion of one end wall of the refrigerant-heating means 6is connected a lower conduit 10 which extends horizontally forcommunication with the first indoor heat exchanger, while to the upperportion of the other end of the refrigerant-heating means is connected ahigher conduit III for communication with the second indoor heatexchanger. In the cooling operation, the refrigerant is introduced intothe refrigerant-heating means 6 through the higher conduit 11 anddischarged therefrom through the lower conduit 10, so that therefrigerant is not allowed to be accumulated in the refrigerant-heatingmeans 6. In the heating operation, on the other hand, the refrigerant isintroduced into the refrigerantheating means 6 through the lower conduit10 and discharged through the higher conduit llll, so that apredetermined quantity of the refrigerant is accumulated in therefrigerant-heating means 6 (up to the level a of the underside of thehigher conduit ll).

FIG. 6 shows another form of the refrigerant-heating means in which amounting tube 3 having one end closed is horizontally inserted into therefrigerant-heating means 6 and an electric heater 7 is inserted intothe mounting tube 8 through the open end thereof. On the left hand sideof the refrigerant-heating means 6 is provided a lower conduit l0 l4which extends vertically for communication with the first indoor heatexchanger 3', while on the right-hand side thereof is provided a higherconduit 11 which also extends vertically for communication with thesecond indoor heat exchanger 3". In the heating operation, therefrigerant introduced into the refrigerant-heating means 6 through thelower conduit 10 is accumulated therein up to the level a of the top endof the higher conduit Ill.

FIG. 8 shows still another form of the refrigerant-heating means.According to this form, a hollow mounting tube 8 having an electricheater 7 wound therearound is inserted into the refrigerant-heatingmeans 6 through one end thereof, and the root of the mounting tube andsaid end of the refrigerant-heating means are soldered together toprovide a liquid-tight sealing l2 or 12'. A higher conduit II isconnected to the top wall of the refrigerant-heating means 6, while alower conduit 10 is connected horizontally to the other end of saidrefrigerantheating means in coaxial relation thereto. In the heatingoperation and defrosting operation, the refrigerant introduced into therefrigerant-heating means 6 through the lower conduit 10 is directlyheated by the electric heater 7 and discharged therefrom through thehigher conduit 11.

Next, the electric circuit of the air conditioner according to theinvention will be described with reference to FIG. 3.

The electric circuit of the air conditioner includes an operating switchSW by which the operation of the air conditioner is switched from onecondition to another among "Off," Fan," High Cool," Low Cool, HighHeat," and Low Heat. The operating switch SW has a power source primaryterminal b, a secondary terminal 11 which is connected with the primaryterminal b during the High Heat" and Low Heat" operations, and an othersecondary terminal 1' which is connected with the primary terminal bduring the High Heat operation only. The primary terminal b of theoperating switch SW is connected with a terminal X of a power source,whereas the secondary terminal h thereof is connected with a closingterminal n of a temperature controller TC for controlling the operationof the compressor, which closing terminal is opened when the roomtemperature is high and closed when the room temperature is low. Acontact p of the temperature controller TC is connected with the otherterminal Y of the power source through a compressor motor MC. Anelectromagnetic coil MR of an electromagnetic relay for controlling theoperation of the electric heater 7 is connected in parallel with thecompressor motor MC. The secondary terminal 1' of the operating switchSWextends to an operating circuit which extends from the electric heater7 to the source terminal Y through the overheat-preventing members FSand TFU and the contact MR which is closed when the electromagneticcoiled MR is energized and opened when the same is not energized. Thus,the electric heater 7, inserted into the refrigerantheating means 6, isenergized only when the compressor is in operation in the heating cycle.

The operating switch SW is also provided with a secondary terminal fwhich is connected with the primary terminal b during the coolingoperation only. The secondary terminal f connected with source terminalY through an electromagnetic coil SV of the four-way change over valve 2which switches the refrigeration cycle to the cooling cycle whenenergized and to the heating cycle when deenergized. Further, thesecondary contact f of the operating switch SW is connected with aclosing contact t of a defrosting switch DC which contact t is closedwhen the outdoor heat exchanger 5 is frosted and opened when the same isnot frosted. A pole contact x of the defrosting switch DC is connectedwith the source terminal X. Because of the construction of the operatingcircuit as described above, when the operating switch SW is in the Heat"position, the four-way changeover valve 2 is held in the position ofcooling cycle and the electric heater 7 is energized.

Further, the operating switch SW is provided with a primary terminal aand a secondary terminal d which will be connected with said primaryterminal a only in the heating operation. The primary terminal a isconnected with the source terminal X and the secondary terminal d of theoperating switch SW is connected with a pole contactj of a switch TCwhich controls the number of revolutions ofa fan according to thetemperature of the refrigerant gas discharged from the compressor 1 orthe temperature of the air blown into the room. A closing contact k ofthe switch TC which is closed when the discharging air temperature islow and opened when the discharging air temperature is high, isconnected with a low speed rotation tenninal y of a fan motor FF. Aclosing contact I of the switch TC is connected with a high speedrotation ter minal y, said closing contact I being opened when the roomtemperature is low and closed when the room temperature is high.Further, a common terminal z of the fan motor is connected with thesource terminal Y. Thus, when the discharging air temperature is low atthe start of the heating operation, the current is supplied to thelow-speed rotation terminal y of the fan motor to rotate the fan at alow speed and thereby to relief the cold draft. On the other hand, whenthe discharging air temperature has risen, the current is supplied tothe highspeed rotation terminal y of the fan motor to rotate the fan ata high speed and thereby to increase the heating capacity.

The circuit connecting the secondary terminal i of the operating switchSW with the electric heater 7 has inserted therein a temperaturecontroller TC which closes the circuit to energize the electric heater 7when the room temperature is low and opens the same to deenergize theelectric heater when the room temperature is high.

The air conditioner of the present invention, having the constructiondescribed in detail hereinabove, has the following advantages: First ofall, by the provision of the refrigerant heating unit 6, the heatingcapacity of the air conditioner is increased by the heat generated bythe electric heater 7, as compared with the conventional heat pump typeair conditioner. Namely, in FIG. 2, as contrasted to the heatingcapacity of the conventional air conditioner which is [(i,,i,,) X thequantity of the refrigerant circulated], that of the present airconditioner is [(i,,i X the quantity of the refrigerant circulatedgreater than the former and is (i i )+(i,,i X the quantity of therefrigerant circulated], which represents a marked increase in theheating capacity.

According to the present invention, the electric heater 7 is disposedwithin the mounting tube 8 of the refrigerant-heating means 6 and theheated portion of the mounting tube 8 is contact with the liquidrefrigerant for exchanging heat with the liquid refrigerant as shown inFIGS. 5,6, and 7. Therefore, the heat transfer rate is high and furtherthere is no danger of fire as the heater is not directly exposed to air.In addition, such arrangement facilitates removal, repair andreplacement of the electric heater 7 upon failure of said electricheater. The same is true when the overheat preventing member 9 isprovided in the mounting tube 8 adjacent the electric heater 7.Furthermore, since the liquid refrigerant is heated by the electricheater 7, the air in the vicinity of the indoor heat exchanger 3 willnot be heated abnormally, which ensures the safety of the airconditioner. The safety will be further ensured if a heat-insulatingmaterial is provided around the outer surface of the refrigerant-heatingmeans 6. The overheatpreventing member 9 for controlling the currentsupply to the electric heater 7 can detect the temperature of themounting tube 8 by direct contact therewith, so that it is much moresensitive in detecting ability and more reliable in operation than theconventional safety device which detects the temperature through theintermediary of air, and hence the danger of fire can be eliminated morepositively.

The electromagnetic relay MR is inserted in the electric circuit of thecompressor 1 so that the electric heater 7 may be energized only afterthe compressor 1 is placed in motion. Therefore, in no case is theelectric heater 7 energized, with the compressor being inoperative. Ifthe refrigerant stops flowing or the flow rate of the refrigerant isreduced, less heat is transferred to the refrigerant and more heat istransferred to the overheat-preventing member 9 from the electric heater7, so that the current supply to the electric heater 7 is automaticallyinterrupted by the action, for example, of a bimetal of said member 9.Since the electric heater 7 is surrounded by the liquid refrigerant, theremaining heat of the electric heater 7 is absorbed by the liquidrefrigerant after the heat pump operation has been stopped, whereby thesubsequent temperature rise of the refrigerant and lubricant isprevented to avoid deterioration and thermal decomposition of the same,providing for safety operation of the air conditioner.

As stated previously, to the refrigerant-heating means 6 are connectedone ends of the lower conduit 10 and the higher conduit 11, the otherends of which are connected to the first indoor heat exchanger 3' andthe second indoor heat exchanger 3 respectively, and when the airconditioner is in the cooling cycle, with the refrigerant circulating inthe directions of the dotted line arrows in FIG. I, the refrigerant isadmitted into the refrigerant-heating means 6 through the higher conduit11 and discharged therefrom through the lower conduit 10, so that it isnot permitted to reside in said refrigerant-heating means, whereas whenthe air conditioner is in the heating cycle with the refrigerantcirculating in the directions of the solid lines arrows, the refrigerantis enters the refrigerant-heating means 6 through the lower conduit 10and leaves the same through the higher conduit 11, so that it isaccumulated in said heating means up to the level of the higher conduitas indicated by the phantom line a in FIGS. 5 to 7. Thus, the quantityof refrigerant in the heating operation is automatically controlled bythe refrigerant-heating means 6 which holds excess refrigerant therein,to the level actually required for the heating operation and therebyreturn flow of the liquid refrigerant into the compresssor l isprevented when the outside temperature is low.

Now, let it be supposed that the refrigerant-heating means of theconstruction shown in FIG. 6 is mounted slantingly. In this .case, thequantity of the refrigerant residing in the refrigerant-heating means isdetermined by the position of the open top end of the higher conduit 11and hence a calculated quantity of the refrigerant cannot be reserved inthe refrigerant-heating means 6, which will result in unsatisfactoryheating operation. Such disadvantage can be obviated by employing therefrigerant-heating means of the construction shown in FIG. 7. In thisrefrigerant-heating means, a higher conduit 11 is provided centrally ofthe heating means and two lower conduits 10 are provided parallelly atthe opposite end portions of the same, so that the quantity of therefrigerant residing in the heating means is always constant.

The air conditioner of the present invention also has such a remarkableadvantage that the defrosting period can drastically be shortened ascompared with the conventional one. Namely, when the outside temperatureis low, the evaporating temperature is lowered and the surfacetemperature of the outdoor heat exchanger 5 drops below the freezingpoint, with the accompanying result that the surface of said outdoorheat exchanger is frosted. In this case, the operation of the airconditioner is switched to the cooling cycle to remove the frost fromthe outdoor heat exchanger. According to the present invention, theelectric heater 7 is energized to heat the refrigerant and therefrigerant is not accumulated in the refrigerant heating means duringthe period of cooling cycle. Therefore, the gaseous refrigerant heatedby the electric heater 7 is forcibly returned to the compressor 1, sothat defrosting can be attained in a short period of time, which in thepast has taken a long time due to a gasless operation.

Describing in further detail, the defrosting operation in normallyperformed upon stopping the fan. This is for the purposes of avoiding acold draft and easing the defrosting operation conducted at the outsidetemperature below the freezing point. However, if the defrostingoperation is performed with the fan being held stationary, the capacityof the indoor heat exchanger 3 becomes shorted, with the result that theevaporating temperature and, therefore, the condensating temperature arelowered. Therefore, the quantity of heat available for defrosting issmall. Furthermore, the liquid refrigerant which has not been evaporatedin the indoor heat exchanger 3 objeetionably flows back into thecompressor 1. According to the present invention, however, heat isimparted to the refrigerant in the indoor heat exchanger 3, so that theevaporating temperature is not lowered, recycling of the liquidrefrigerant into the compressor 1 can be avoided, the condensatingtemperature is not lowered, and a large quantity of heat is availablefor defrosting. Thus, the defrosting operation can be accomplished in ashort period of time and the efficiency of the heating operation can beenhanced.

Still another advantage of the present air conditioner is thatoccurrence of a cold draft can completely be avoided in the heatingoperation, since the electric circuit thereof is so designed that thespeed of the fan is controlled according to the room temperature.

Another important advantage of the present air conditioner is that theroom can be heated efficiently with less power consumption, due to thefact that in the heating operation the air conditioner is operated onlyin the heating cycle,. with the electric heater 7 being energized whenthe room temperature is low and is deenergized when the room temperatureis high.

The characteristics of the air conditioner of the present invention willhereinafter be explained, which were actually measured on a 0.75 kw.window-type room cooler of the construction shown in FIG. 4, which isprovided with a heater and in which the present invention is embodied.

FIG. 9 shows the relationship between the outdoor temperature, and theheating capacity and power consumption, in each of the cases when theheat pump only was used and the case when both the heat pump and theheater were used. In the test, the room-heating capacity was measured bymeasuring the temperature rise of cold water coil placed in the room,using the room-type calorimeter specified in Appendix I of C-6912(Electric Air Conditioners) of Japan Industrial Standards. The diagramof FIG. 9 shows that a desired heating capacity of 2,240 kcaL/h (60cycle) at an outdoor temperature of -2 C was obtained by incorporatingin the refrigerant heating means an electric heater having a capacity of0.7 kw. This capacity of the electric heater is much smaller as comparedwith a capacity of 2.6 kw. which is required for obtaining the sameheating capacity with an electric heater only.

FIG. 10 shows the effect of reserving the refrigerant in therefrigerant-heating means 6. The temperature of the suction pipe to thecompressor was measured at the locations indicated. As will be seen fromthe diagram, when the refrigerant is reserved in the refrigerant-heatingmeans, the refrigerant is sucked into the compressor in the form of asuperheated gas at a lower outdoor temperature than when the refrigerantis not reserved.

FIG. 11 shows the condition of the present air conditioner in thedefrosting operation. As shown, the defrosting operation is completed inabout minutes when the operation is performed under the conditionsspecified in ARI (Air-Conditioning and Refrigeration Institute)Specification. This represents a marked reduction in defrosting periodas compared with about to 25 minutes which is required by theconventional air conditioner which is not provided with an electricheater to heat the refrigerant nor with means for reserving therefrigerant. In comparison with the defrosting operation period of 4hours specified in the defrosting operation test specified in ARIStandard 240, the defrosting operation period according to the presentinvention is about 5 minutes which is much smaller than percent of thespecified value. Furthermore, when the heat pump was again set inmotion, the discharging air temperature rised from the initial value of21 C. (70 F.) to 32 C. (about 90 F.) and was maintained at saidtemperature throughout the prescribed period of operation, which is farhigher than the specified lower limit of l8.5 C. (65 F.) All of thesevalues are acceptable to the ARI Standard.

FIG. I2 is concerned with the safety of the refrigerant-heating meansand shows how the inside and outside temperatures of therefrigerant-heating means change with time, when the fan and thecompressor are stopped. The function of the overheat-preventing memberwas tested under such severe conditions that the electric heater is heldenergized while the fan and the compressor are held inoperative, whichwill not actually occur. The temperature of the heater surface incontact with the refrigerant, which is highest, was measured by means ofa thermocouple welded to said surface. The result was that thetemperature of the heater surface reached the highest value and was 130C. 2 minutes after the heater had been deenergized by the action of theoverheat-preventing member. It is revealed in the literatures relatingto refrigerant that such temperature will not have a practical effect ofdeteriorating the refrigerant and lubricant at all if it lasts only fora short period.

What we claim is:

l. A heat pump system air conditioner having a heat pump system coolingand heating circuit operating in a refrigeration cycle and composed of acompressor 1, four-way changeover valve 2, an indoor heat exchanger 3consisting of a first indoor heat exchanger 3 and a second indoor heatexchanger 3"an expansion member (4), an outdoor heat exchanger 5 and anaccumulator 14, in which a refrigerant-heating means (6) having anelectric heater 7 inserted therein in such a manner that it is notexposed to air is provided between the first indoor heat exchanger 3'and the second indoor heat exchanger 3"so that the heating operation hasa refrigerant partially or wholly condensed in the first indoor heatexchanger 3' is heated and evaporated in said refrigerant-heating meansand then condensed again in the second indoor heat exchanger 3"wherebythe air circulating in a room to be heated can be heated by the heatgenerated by the condensation of the gaseous refrigerant in the indoorheat exchanger 3 plus the heat generated by the electric heater 7.

2. A heat pump system air conditioner as defined in claim I, wherein inthe refrigerant-heating means a conduit for introducing the refrigerantfrom the first indoor heat exchanger 3' into the refrigerant-heatingmeans 6 therethrough is open in the lower portion of saidrefrigerant-heating means 6, whereas a conduit 11 for discharging therefrigerant from the refrigerant-heating means 6 into the second indoorheat exchanger (3") therethrough is open in the upper portion of therefrigerant-heating means 6, whereby in the heating operation thequantity of the refrigerant substantially acting as refrigerant in therefrigeration cycle is reduced by storing the liquid refrigerant in therefrigerant-heating means 6 to enhance the efiiciency of the heatingoperation, whereas in the cooling operation the refrigerant is notallowed to reside in the refrigerant-heating means 6 so that coolingoperation can be attained at a high efficiency.

3. A heat pump system air conditioner as defined in claim 2, wherein inthe refrigerant-heating means a mounting tube 8 is extended through saidrefrigerant heating means, with one end open to the outside of one endof the refrigerant-heating means 6, and said electric heater (7) and anoverheat-preventing member 9 such as a thermostat or a temperature fusefor preventing overheating of the outer peripheral surface of saidmounting tube 8 in contact with the refrigerant are inserted into saidmounting tube 8, whereby deterioration of the refrigerant passingthrough said refrigerant-heating means 6 is prevented.

4. A heat pump system air conditioner as defined in claim 3, whereinradiator fins 13 are provided on the outer peripheral surface of saidmounting tube 8.

5 A heat pump system air conditioner as defined in claim 2, wherein inthe refrigerant-heating means said electric heater 7 is directlyinserted into the refrigerant within the refrigerantheating means 6 fordirect heat exchanging between the refrigerant and the electric heater7.

6. A heat pump system air conditioner as defined in claim 2, wherein aheat-insulating material is applied onto the outer peripheral surface ofsaid refrigerant-heating means 6 to render said refrigerant-heatingmeans fire-proof.

7. A heat pump system air conditioner as defined in claim 2, wherein anoperating switch SW is provided to switch the operation of the airconditioner from one another among the conditions ofOff," Fan, I-IighCold," Low Cold, High Heat" and Low Heat said operating switch SW beingprovided with a primary terminal b connectedto one terminal X of a powersource and a secondary terminal I: or i which will be connected to saidprimary terminal b only in the heating operation, said secondaryterminal h or i being connected with a closing contact n of atemperature controller TC for controlling the operation of thecompressor, which closing contact n is opened when the room temperatureis high and closed when the room temperature is low, a pole contact p ofsaid temperature controller TC being connected with the other powersource terminal Y through a compressor motor MC, said compressor motorMC having connected in parallel thereto an electromagnetic coil MR of anelectromagnetic relay for controlling the operation of the electricheater 7, and

said secondary terminal h of i of said operating switch SW I beingconnected with the power source terminal Y through the electric heater 7and the contact MR is parallel to the circuit extending from saidsecondary terminal h or i to the power source terminal Y through saidcompressor motor MC, which contact MR is closed when the electromagneticcoil MR is energized and opened when the electromagnetic coil is notenergized, whereby the electric heater (7) inserted in therefrigerant-heating means 6 is energized only when the compressor is inmotion in the heating operation.

8. A heat pump system air conditioner as defined in claim 7, wherein theoperating switch SW is provided with a secondary terminal f which willbe connected with the primary terminal b only in the cooling operation,said secondary terminal f being connected with the power source terminalY through an electromagnetic coil SV of the four-way changeover valve(2) which shifts the refrigeration cycle to the cooling cycle whenenergized and to the heating cycle when not energized, further saidsecondary contact f being connected with a closing contact t of adefrosting switch DC which closing contact 1 is closed when the outdoorheat exchanger 5 is frosted and opened when the same is not frosted, anda pole contact x of said defrosting switch DC being connected with thepower source terminal X, whereby when the operating switch SW is held inthe Heat" position, the four-way changeover valve 2 is placed in aposition for the cooling cycle and the electric heater (7 is heldenergized also in the defrosting operation.

9. A heat pump system air conditioner as defined in claim 7, wherein theoperating switch SW is provided with a primary terminal a connected withone terminal X of a power source and a secondary terminal d which willbe connected with said primary terminal a in the heating operation, saidsecondary terminal d being connected with a pole contactj of a switch TCwhich controls the number of revolutions of a fan according to thetemperature of the air blowing into the room upon detecting thetemperature of the gaseous refrigerant discharged from the compressor 1or the temperature of the discharging air, a closing contact k saidswitch TC; being connected with a low speed rotation terminal y ofa fanmotor MF, which closing contact k is closed when the discharging airtemperature is low and opened when the discharging air temperature ishigh, a closing contact I of said switch TC being connected with ahigh-speed rotation terminal y the fan motor which closing contact I isopened when the room temperature is low and closed when the roomtemperature is high, and further a common terminal z of said fan motorbeing connected with the power source terminal Y, whereby when thedischarging air temperature is low in the initial stage of the heatingoperation, a current is conducted to the low-speed rotation terminal yof the fan motor to drive the fan at a low speed and thereby to remedythe cold draft blowing into the room, whereas when the draft temperaturehas risen upon passage of time, the current is conducted to thehigh-speed rotation terminal y' of the fan motor to drive the fan at ahigh speed and thereby to increase the heating capacity of theconditionerr l0.,A heat pump system air conditioner as defined in claim7, wherein a temperature controller TC, for controlling the electricheater is inserted in the circuit connecting the secondary terminal h ori of the operating switch SW with the electric heater 7 so as to closethe circuit when the room temperature is low and open the same when theroom temperature is high, whereby the electric heater (7) is usedeffectively.

1. A heat pump system air conditioner having a heat pump system coolingand heating circuit operating in a refrigeration cycle and composed of acompressor 1, four-way changeover valve 2, an indoor heat exchanger 3consisting of a first indoor heat exchanger 3'' and a second indoor heatexchanger 3'''' an expansion member (4), an outdoor heat exchanger 5 andan accumulator 14, in which a refrigerant-heating means (6) having anelectric heater 7 inserted therein in such a manner that it is notexposed to air is provided between the first indoor heat exchanger 3''and the second indoor heat exchanger 3'''' so that the heating operationhas a refrigerant partially or wholly condensed in the first indoor heatexchanger 3'' is heated and evaporated in said refrigerant-heating meansand then condensed again in the second indoor heat exchanger 3''''whereby the air circulating in a room to be heated can be heated by theheat generated by the condensation of the gaseous refrigerant in theindoor heat exchanger 3 plus the heat generated by the electric heater7.
 2. A heat pump system air conditioner as defined in claim l, whereinin the refrigerant-heating means a conduit 10 for introducing therefrigerant from the first indoor heat exchanger 3'' into therefrigerant-heating means 6 therethrough is open in the lower portion ofsaid refrigerant-heating means 6, whereas a conduit 11 for dischargingthe refrigerant from the refrigerant-heating means 6 into the secondindoor heat exchanger (3'''') therethrough is open in the upper portionof the refrigerant-heating means 6, whereby in the heating operation thequantity of the refrigerant substantially acting as refrigerant in therefrigeration cycle is reduced by storing the liquid refrigerant in therefrigerant-heating means 6 to enhance the efficiency of the heatingoperation, whereas in the cooling operation the refrigerant is notallowed to reside in the refrigerant-heating means 6 so that coolingoperation can be attained at a high efficiency.
 3. A heat pump systemair conditioner as defined in claim 2, wherein in therefrigerant-heating means a mounting tube 8 is extended through saidrefrigerant heating means, with one end open to the outside of one endof the refrigerant-heating means 6, and said electric heater (7) and anoverheat-preventing member 9 such as a thermostat or a temperature fusefor preventing overheating of the outer peripheral surface of saidmounting tube 8 in contact with the refrigerant are inserted into saidmounting tube 8, whereby deterioration of the refrigerant passingthrough said refrigerant-heating means 6 is prevented.
 4. A heat pumpsystem air conditioner as defined in claim 3, wherein radiator fins 13are provided on the outer peripheral surface of said mounting tube
 8. 5.A heat pump system air conditioner as defined in claim 2, wherein in therefrigerant-heating means said electric heater 7 is directly insertedinto the refrigerant wiThin the refrigerant-heating means 6 for directheat exchanging between the refrigerant and the electric heater
 7. 6. Aheat pump system air conditioner as defined in claim 2, wherein aheat-insulating material is applied onto the outer peripheral surface ofsaid refrigerant-heating means 6 to render said refrigerant-heatingmeans fire-proof.
 7. A heat pump system air conditioner as defined inclaim 2, wherein an operating switch SW is provided to switch theoperation of the air conditioner from one another among the conditionsof ''''Off,'''' ''''Fan,'''' ''''High Cold,'''' ''''Low Cold,''''''''High Heat'''' and ''''Low Heat'''' said operating switch SW beingprovided with a primary terminal b connected to one terminal X of apower source and a secondary terminal h or i which will be connected tosaid primary terminal b only in the heating operation, said secondaryterminal h or i being connected with a closing contact n of atemperature controller TC1 for controlling the operation of thecompressor, which closing contact n is opened when the room temperatureis high and closed when the room temperature is low, a pole contact p ofsaid temperature controller TC1 being connected with the other powersource terminal Y through a compressor motor MC, said compressor motorMC having connected in parallel thereto an electromagnetic coil MR of anelectromagnetic relay for controlling the operation of the electricheater 7, and said secondary terminal h of i of said operating switch SWbeing connected with the power source terminal Y through the electricheater 7 and the contact MR is parallel to the circuit extending fromsaid secondary terminal h or i to the power source terminal Y throughsaid compressor motor MC, which contact MR is closed when theelectromagnetic coil MR is energized and opened when the electromagneticcoil is not energized, whereby the electric heater (7) inserted in therefrigerant-heating means 6 is energized only when the compressor is inmotion in the heating operation.
 8. A heat pump system air conditioneras defined in claim 7, wherein the operating switch SW is provided witha secondary terminal f which will be connected with the primary terminalb only in the cooling operation, said secondary terminal f beingconnected with the power source terminal Y through an electromagneticcoil SV of the four-way changeover valve (2) which shifts therefrigeration cycle to the cooling cycle when energized and to theheating cycle when not energized, further said secondary contact f beingconnected with a closing contact t of a defrosting switch DC whichclosing contact t is closed when the outdoor heat exchanger 5 is frostedand opened when the same is not frosted, and a pole contact x of saiddefrosting switch DC being connected with the power source terminal X,whereby when the operating switch SW is held in the ''''Heat''''position, the four-way changeover valve 2 is placed in a position forthe cooling cycle and the electric heater (7) is held energized also inthe defrosting operation.
 9. A heat pump system air conditioner asdefined in claim 7, wherein the operating switch SW is provided with aprimary terminal a connected with one terminal X of a power source and asecondary terminal d which will be connected with said primary terminala in the heating operation, said secondary terminal d being connectedwith a pole contact j of a switch TC3 which controls the number ofrevolutions of a fan according to the temperature of the air blowinginto the room upon detecting the temperature of the gaseous refrigerantdischarged from the compressor 1 or the temperature of the dischargingair, a closing contact k said switch TC3 being connected with a lowspeed rOtation terminal y of a fan motor MF, which closing contact k isclosed when the discharging air temperature is low and opened when thedischarging air temperature is high, a closing contact l of said switchTC3 being connected with a high-speed rotation terminal y'' the fanmotor which closing contact l is opened when the room temperature is lowand closed when the room temperature is high, and further a commonterminal z of said fan motor being connected with the power sourceterminal Y, whereby when the discharging air temperature is low in theinitial stage of the heating operation, a current is conducted to thelow-speed rotation terminal y of the fan motor to drive the fan at a lowspeed and thereby to remedy the cold draft blowing into the room,whereas when the draft temperature has risen upon passage of time, thecurrent is conducted to the high-speed rotation terminal y'' of the fanmotor to drive the fan at a high speed and thereby to increase theheating capacity of the conditioner.
 10. A heat pump system airconditioner as defined in claim 7, wherein a temperature controller TC2for controlling the electric heater is inserted in the circuitconnecting the secondary terminal h or i of the operating switch SW withthe electric heater 7 so as to close the circuit when the roomtemperature is low and open the same when the room temperature is high,whereby the electric heater (7) is used effectively.